The first depiction of this constellation in a celestial atlas was in German cartographer Johann Bayer's Uranometria of 1603.[2] De Houtman included it in his southern star catalogue the same year under the Dutch name De Pauww, "The Peacock".[3]

Pavo and the nearby constellations Phoenix, Grus and Tucana are collectively called the "Southern Birds".[4]

The peacock in Greek mythology[edit]

According to Mark Chartrand, former executive director of the National Space Institute, Plancius may not have been the first to designate this group of stars as a peacock: "In Greek myth the stars that are now the Peacock were Argos [or Argus], builder of the ship Argo. He was changed by the goddess Juno into a peacock and placed in the sky along with his ship."[6][7] Indeed, the peacock "symboliz[ed] the starry firmament" for the Greeks,[8] and the goddess Hera was believed to drive through the heavens in a chariot drawn by peacocks.[9]

The peacock and the "Argus" nomenclature are also prominent in a different myth, in which Io, a beautiful princess of Argos, was lusted after by Zeus (Jupiter). Zeus changed Io into a heifer to deceive his wife (and sister) Hera and couple with her. Hera saw through Zeus's scheme and asked for the heifer as a gift. Zeus, unable to refuse such a reasonable request, reluctantly gave the heifer to Hera, who promptly banished Io and arranged for Argus Panoptes, a creature with one hundred eyes, to guard the now-pregnant Io from Zeus. Meanwhile, Zeus entreated Hermes to save Io; Hermes used music to lull Argus Panoptes to sleep, then slew him. Hera adorned the tail of a peacock—her favorite bird—with Argus's eyes in his honor.[10][11]

As recounted in Ovid's Metamorphoses, the death of Argus Panoptes also contains an explicit celestial reference: "Argus lay dead; so many eyes, so bright quenched, and all hundred shrouded in one night. Saturnia [Hera] retrieved those eyes to set in place among the feathers of her bird [the peacock, Pavo] and filled his tail with starry jewels."[12]

It is uncertain whether the Dutch astronomers had the Greek mythos in mind when creating Pavo but, in keeping with other constellations introduced by Plancius through Keyser and De Houtmann, the "peacock" in the new constellation likely referred to the green peacock, which the explorers would have encountered in the East Indies, rather than the blue peacock known to the ancient Greeks.[13]

Equivalents in other cultures[edit]

Characteristics[edit]

Pavo is bordered by Telescopium to the north, Apus and Ara to the west, Octans to the south, and Indus to the east and northeast. Covering 378 square degrees, it ranks 44th of the 88 modern constellations in size and covers 0.916% of the night sky.[15] The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Pav".[16] The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of 10 segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 18h 10.4m and 21h 32.4m, while the declination coordinates are between −56.59° and −74.98°.[1] As one of the deep southern constellations, it remains below the horizon at latitudes north of the 30th parallel in the Northern Hemisphere, and is circumpolar at latitudes south of the 50th parallel in the Southern Hemisphere.[17] Some of the stars in the constellation form an asterism known as "the Saucepan" in Australia when they are used for navigation, as they point toward the southern celestial pole.[18]

Notable features[edit]

Stars[edit]

Although he depicted Pavo on his chart, Bayer did not assign its stars Bayer designations. French explorer and astronomer Nicolas Louis de Lacaille labelled them Alpha to Omega in 1756, but omitted Psi and Xi, and labelled two pairs of stars close together Mu and Phi Pavonis. In 1879, American astronomer Benjamin Gould designated a star Xi Pavonis as he felt its brightness warranted a name, but dropped Chi Pavonis due to its faintness.[19]

With an apparent magnitude of 3.43, Beta Pavonis is the second-brightest star in the constellation. A white giant of spectral class A7III,[23] it is an aging star that has used up the hydrogen fuel at its core and has expanded and cooled after moving off the main sequence. It lies 135 light years away from our solar system.[24]

Lying a few degrees west of Beta is Delta Pavonis, a nearby Sun-like but more evolved star;[17] this is a yellow subgiant of spectral type G8IV and apparent magnitude 3.56 that is only 19.9 light years distant from Earth.[25] East of Beta and at the constellation's eastern border with Indus is Gamma Pavonis, a fainter, solar-type star 30 light years from Earth with a magnitude of 4.22 and stellar class F9V.[26] Other nearby stars in Pavo are much fainter: SCR 1845-6357 is a binary system with an apparent magnitude of 17.4 consisting of a red dwarf and brown dwarf companion lying around 12.6 light years distant, while Gliese 693 is a red dwarf of magnitude 10.78 lying 19 light years away.[27]

Located in the west of the constellation and depicting the peacock's tail are Eta and Xi Pavonis.[33] At apparent magnitude 3.6, Eta is a luminous orange giant of spectral type K2II some 350 light years distant from Earth.[34] Xi Pavonis is a multiple star system visible in small telescopes as a brighter orange star and fainter white companion.[28] Located around 470 light years from Earth, the system has a magnitude of 4.38.[35] AR Pavonis is a faint but well-studied eclipsing binary composed of a red giant and smaller hotter star some 18000 light years from Earth. It has some features of a cataclysmic variable, the smaller component most likely having an accretion disc.[36] The visual magnitude ranges from 7.4 to 13.6 over 605 days.[37]

Planetary systems and debris disks[edit]

Six stars with planetary systems have been found. Three planets have been discovered in the system of the orange star HD 181433, an inner super-earth with an orbital period of 9.4 days and two outer gas giants with periods of 2.6 and 6 years respectively.[38]HD 196050 and HD 175167 are yellow G-class Sun-like stars, while HD 190984 is an F-class main sequence star slightly larger and hotter than the Sun; all three are accompanied by a gas giant companion.[39][40][41]HD 172555 is a young white A-type main sequence star, two planets of which appear to have had a major collision in the past few thousand years. Spectrographic evidence of large amounts of silicon dioxide gas indicates the smaller of the two, which had been at least the size of Earth's moon, was destroyed, and the larger, which was at least the size of Mercury, was severely damaged. Evidence of the collision was detected by NASA's Spitzer Space Telescope.[42] In the south of the constellation, Epsilon Pavonis is a 3.95-magnitude white main sequence star of spectral type A0Va located around 105 light years distant from Earth.[43] It appears to be surrounded by a narrow ring of dust at a distance of 107 AU.[44]

Meteor showers[edit]

Pavo is the radiant of two annual meteor showers: the Delta Pavonids and August Pavonids. Appearing from 21 March to 8 April and generally peaking around 5 and 6 April, Delta Pavonids are thought to be associated with Comet Grigg-Mellish.[51] This shower was discovered by one Michael Buhagiar from Perth, Australia,[52] who observed meteors on six occasions in eleven years between 1969 and 1980.[53] The August Pavonids peak around August 31 and are thought to be associated with the Halley-type Comet Levy (P/1991 L3).[54]

Notes[edit]

^C6 is equivalent to a class M2–M3 star, the 4 shows the strength of the Swan bands on a scale of 1 (weak) to 5 (strong), and the Nb indicates bands of the chemical element niobium. See:Gray, Richard O.; Corbally, Christopher J. (2009). Stellar Spectral Classification. Princeton, New Jersey: Princeton University Press. p. 309. ISBN978-0-691-12511-4.